Optical information recording media, such as a DVD±R, an HD DVD-R, and a BD-R, have become widespread since it is possible to record or reproduce a large amount of digital data on or from the optical information recording media at a relatively low cost. However, when data can be easily copied, for example, illegal copy discs of music CDs or video files are likely to appear on the market. In addition, in recent years, video or music data has been distributed through a network. Therefore, a means for copyright protection is needed.
As the means for copyright protection, for example, various means, such as a means disclosed in Japanese Patent Laid-open No. 2002-157740 and a means disclosed in Japanese Patent Laid-open No. 2001-110062, have been proposed. In these means, encryption key data or copy protection data is written in a portion of a recording area for copyright protection.    Patent Citation 1: Japanese Patent Laid-open No. 2002-157740    Patent Citation 2: Japanese Patent Laid-open No. 2001-110062